Aseptic automatic packaging machines are used in the packaging of products with fluid behaviour, such as more or less hard particles of a certain size in suspension in a liquid, inside packaging containers of the disposable type. These machines are connected by means of a pipe to units for the processing and the conveyance of the contents to the machine. A pumping unit is typically provided to secure that a uniform and predetermined volume per time unit of products to be packaged flows into the individual container being formed from a tube of packaging material. This pumping unit may be, e.g., a metering pump, which at each cycle distributes the desired and predetermined amount of contents. The hygienic requirements imposed to such a pumping unit are very severe, as the packaging machine is of the aseptic type, i.e., it produces packages which must be filled with contents which have previously undergone a operation to make them sterile.
These requirements are important since the particles contained inside the product can be portions of vegetables, fish, meat and other solid or semi-solid foodstuffs are particularly dangerous if they are not stored under conditions of absolute sterility.
Known pumping units caused many problems for the packaging machine, in that the complete cleaning thereof inside the packaging plant was difficult, and they were hence the staring point for the diffusion of non-aseptic conditions. Their particular structure on one hand created an obstacle to the centralized washing of the packaging machine, and on the other was the starting point for infiltrations from the outside, by not being provided with sufficient aseptic barriers, or showing portions which during the operation process could come into connection, even if minimum, with the non-aseptic outer environment.
Moreover, the particular masses of the pumping body or piston absorbed heat, e.g., during the step of sterilization and washing with superheated steam, which they had a certain difficulty in losing before the restarting of the production and filling cycle.
Not least of the problems was that of a quite obliged positioning thereof relative to the packaging unit of the packaging machine, with some consequent unbalancing or lack in tightness in the subsequent production step due to vibrations, sudden temperature changes, wear of components, with serious difficulties both as for the restoration of the exact matching contacts between the surfaces, and as for the necessary clearances.